core loss

Core loss

The rate of energy conversion into heat in a magnetic material due to the presence of an alternating or pulsating magnetic field. It may be subdivided into two principal components, hysteresis loss and eddy-current loss. See Eddy current

The energy consumed in magnetizing and demagnetizing magnetic material is called the hysteresis loss. It is proportional to the frequency and to the area inside the hysteresis loop for the material used. Most rotating machines are stacked with silicon steel laminations, which have low hysteresis losses. The cores of large units are sometimes built up with cold-reduced, grain-oriented, silicon iron punchings having exceptionally low hysteresis loss, as well as high permeability when magnetized along the direction of rolling.

Induced currents flow within the magnetic material because of variations in the flux; this is called eddy-current loss. For 60-cycle rotating machines, core laminations of 0.014–0.018 in. (0.35–0.45 mm) are usually used to reduce this eddy-current loss. See Electric rotating machinery